Add exception if schema owner cannot be resolved

Author: alex-kulakov

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/Resources/Strings.Designer.cs

@@ -135,4 +135,7 @@
   <data name="ExSchemaXDoesNotExistOrBelongsToAnotherUser" xml:space="preserve">
     <value>Schema '{0}' either does not exist or belongs to another user.</value>
   </data>
+  <data name="ExCantFindSchemaXOwnerWithIdYInTheListOfUsers" xml:space="preserve">
+    <value>Can't find schema '{0}' owner with oid '{1}' in the list of users.</value>
+  </data>
 </root>

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/Resources/Strings.resx

@@ -522,7 +522,12 @@ protected virtual void ReadSchemaData(DbDataReader dataReader, ExtractionContext
         catalog.DefaultSchema = schema;
       }
 
-      schema.Owner = context.UserLookup[owner];
+      if (context.UserLookup.TryGetValue(owner, out var ownerName)) {
+        schema.Owner = ownerName;
+      }
+      else {
+        throw new InvalidOperationException(string.Format(Resources.Strings.ExCantFindSchemaXOwnerWithIdYInTheListOfUsers, name, owner));
+      }
       context.SchemaMap[oid] = schema;
       context.ReversedSchemaMap[schema] = oid;
     }